1. Field of the Invention
The present invention relates to an inflatable cushion. More specifically, this invention relates to an inflatable cushion having shielded seams.
2. Description of Related Art
Inflatable airbags are well accepted for use in motor vehicles and have been credited with preventing numerous deaths and injuries. Some statistics estimate that frontal airbags reduce the fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of a seat belt and an airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Airbag use presents clear benefits and vehicle owners are frequently willing to pay the added expense for airbags. In addition, the inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles.
Airbag systems typically include three principal components: an electronic control unit (ECU), an inflator, and an inflatable cushion. The ECU monitors the acceleration and deceleration of the vehicle and determines when accident conditions exist. The ECU is in communication with the inflator and transmits a signal to the inflator when the ECU determines that the vehicle has been involved in an accident.
In response to receipt of the signal, the inflator generates inflation gas. The inflator can be designed to produce inflation gas using various methods. For instance, the inflator may use pyrotechnic techniques or simply release compressed gas. In addition, the inflator may use a combination of both pyrotechnics and compressed gas to produce pressurized inflation gas. The inflator is in fluid communication with the inflatable cushion.
The inflatable cushion receives the gas generated by the inflator and rapidly expands as the gas fills the cushion. The inflatable cushion is made from a flexible material, such as fabric. When expanded, the cushion is positioned to prevent the occupant from striking hard surfaces within the vehicle, such as the steering wheel, dashboard, or windshield. The inflated cushion receives the energy of an occupant impact and dissipates the energy such that injuries are minimized or avoided. If the occupant is using a seat belt, airbags also assist in retaining the vehicle occupant within the seat belt and minimize the risk of ejection from the vehicle.
The most common type of airbag system stores the cushion and inflator in a compartment in the steering wheel. This type of airbag system is frequently referred to as a driver's side airbag system. When the vehicle is involved in an accident, the cushion receives the gas generated by the inflator, expands, and is propelled out of the compartment in the steering wheel. The cushion is fully inflated in a fraction of a second. The inflated cushion prevents the driver from striking the steering wheel and dissipates the kinetic energy of the occupant to minimize injury to the occupant. Similar airbag systems are frequently installed in the passenger's side of the dashboard.
More recently, inflatable curtains have been used to protect vehicle occupants. Prior to deployment, inflatable curtains are generally stored in a compartment located above the side doors of the vehicle. When inflation gas is injected into the curtain, the curtain deploys in a downward direction to prevent the occupant from striking the side windows or doors of the vehicle during an accident.
Other types of airbag systems are currently in development or use. For example, a knee bolster airbag system is generally positioned below the dashboard in a passenger vehicle in a stowed condition and deploys to protect an occupant's lower extremities and knees.
Regardless of the type of airbag in use, the inflatable cushion in use must expand rapidly to provide the desired protection to a vehicle occupant in an accident. This rapid expansion places significant structural stress on the cushion during the inflation process. The elevated temperature of gas injected into the cushion, coupled with the structural stress placed on the cushion during inflation, can result in cushion deterioration. Moreover, in recent times, the gas temperature of new inflator technologies has generally increased.
Cushion seams, where panels of the cushion are sewn or otherwise secured together, are particularly vulnerable to damage during the inflation process. It has been observed that as a cushion is pressurized, the woven yarns of the fabric pull away from each other at points where the sewn threads pass through the fabric, allowing hot gas to erode the fabric yarns. This type of cushion deterioration is often referred to as seam “combing.”
Many different systems have been implemented in an attempt to address this problem. For example, cushion fabrics have been treated with a heat-resistant coating, such as silicone or urethane. Unfortunately, coating the cushion fabric is expensive and time consuming. Other cushion heat-shielding systems have also been developed. However, these systems are generally complex and require significant time to install in the cushions.
Accordingly, there is a need in the art for an inflatable cushion that addresses one or more of the above-listed problems. Such a cushion is disclosed herein.